William W. Darrow

National Case-Control Study of Kaposi's Sarcoma and Pneumocystis carinii Pneumonia in Homosexual Men: Part 1, Epidemiologic Results

To identify risk factors for the occurrence of Kaposis sarcoma and Pneumocystis carinii pneumonia in homosexual men, we conducted a case-control study in New York City, San Francisco, Los Angeles, and Atlanta. Fifty patients (cases) (39 with Kaposis sarcoma, 8 with pneumocystis pneumonia, and 3 with both) and 120 matched homosexual male controls (from sexually transmitted disease clinics and private medical practices) participated in the study. The variable most strongly associated with illness was a larger number of male sex partners per year (median, 61 for patients; 27 and 25 for clinic and private practice controls, respectively). Compared with controls, cases were also more likely to have been exposed to feces during sex, have had syphilis and non-B hepatitis, have been treated for enteric parasites, and have used various illicit substances. Certain aspects of a lifestyle shared by a subgroup of the male homosexual population are associated with an increased risk of Kaposis sarcoma and pneumocystis pneumonia.

Social networks and infectious disease: The Colorado Springs study

The social network paradigm provides a set of concepts and methods useful for studying the structure of a population through which infectious agents transmitted during close personal contact spread, and an opportunity to develop improved disease control programs. The research discussed was a first attempt to use a social network approach to better understand factors affecting the transmission of a variety of pathogens, including hepatitis B virus (HBV) and human immunodeficiency viruses (HIV), in a population of prostitutes, injecting drug users (IDU) and their personal associates in a moderate-sized city (Colorado Springs, CO). Some of the challenges of studying large social networks in epidemiological research are described, some initial results reported and a new view of interconnections in an at risk population provided. Overall, for the first time in epidemiologic research a large number of individuals (over 600) were found connected to each other, directly or indirectly, using a network design. The average distance (along observed social relationships) between persons infected with HIV and susceptible persons was about three steps (3.1) in the core network region. All susceptibles in the core were within seven steps of HIV infection.

Course of HIV-I infection in a cohort of homosexual and bisexual men: An 11 year follow up study

OBJECTIVE--To characterise the natural history of sexually transmitted HIV-I infection in homosexual and bisexual men. DESIGN--Cohort study. SETTING--San Francisco municipal sexually transmitted disease clinic. PATIENTS--Cohort included 6705 homosexual and bisexual men originally recruited from 1978 to 1980 for studies of sexually transmitted hepatitis B. This analysis is of 489 cohort members who were either HIV-I seropositive on entry into the cohort (n = 312) or seroconverted during the study period and had less than or equal to 24 months between the dates of their last seronegative and first seropositive specimens (n = 177). A subset of 442 of these men was examined in 1988 or 1989 or had been reported to have developed AIDS. MAIN OUTCOME MEASURES--Development of clinical signs and symptoms of HIV-I infection, including AIDS, AIDS related complex, asymptomatic generalised lymphadenopathy, and no signs or symptoms of infection. MEASUREMENTS AND MAIN RESULTS--Of the 422 men examined in 1988 or 1989 or reported as having AIDS, 341 had been infected from 1977 to 1980; 49% (167) of these men had died of AIDS, 10% (34) were alive with AIDS, 19% (65) had AIDS related complex, 3% (10) had asymptomatic generalised lymphadenopathy, and 19% (34) had no clinical signs or symptoms of HIV-I infection. Cumulative risk of AIDS by duration of HIV-I infection was analysed for all 489 men by the Kaplan-Meier method. Of these 489 men, 226 (46%) had been diagnosed as having AIDS. We estimated that 13% of cohort members will have developed AIDS within five years of seroconversion, 51% within 10 years, and 54% within 11.1 years. CONCLUSION--Our analysis confirming the importance of duration of infection to clinical state and the high risk of AIDS after infection underscores the importance of continuing efforts both to prevent transmission of HIV-I and to develop further treatments to slow or stall the progression of HIV-I infection to AIDS.

Social network dynamics and HIV transmission.

Objective:To prospectively study changes in the social networks of persons at presumably high risk for HIV in a community with low prevalence and little endogenous transmission. Methods:From a cohort of 595 persons at high risk (prostitutes, injecting drug users, and sexual partners of these persons) and nearly 6000 identified contacts, we examined the social networks of a subset of 96 persons who were interviewed once per year for 3 years. We assessed their network configuration, network stability, and changes in risk configuration and risk behavior using epidemiologic and social network analysis, and visualization techniques. Results:Some significant decrease in personal risk-taking was documented during the course of the study, particularly with regard to needle-sharing. The size and number of connected components (groups that are completely connected) declined. Microstructures (small subgroups of persons that interact intensely) were either not present, or declined appreciably during the period of observation. Conclusions:In this area of low prevalence, the lack of endogenous transmission of HIV may be related in part to the lack of a network structure that fosters active propagation, despite the continued presence of risky behaviors. Although the relative contribution of network structure and personal behavior cannot be ascertained from these data, the study suggests an important role for network configuration in the transmission dynamics of HIV.

The Acquired Immunodeficiency Syndrome in a Cohort of Homosexual Men: A Six-Year Follow-up Study

A cohort of 6875 homosexual men, initially seen at the San Francisco City Clinic between 1978 and 1980, were studied to determine the incidence and prevalence of the acquired immunodeficiency syndrome, related conditions, and infection with the human T-lymphotropic virus, type III/lymphadenopathy-associated virus (HTLV-III/LAV). By December 1984, 2.4% of the men had the syndrome; mortality attributable to the syndrome in 1984 was 600/100 000. For each man with the syndrome in a representative sample of 474 cohort members seen in 1984, 7.5 men had generalized lymphadenopathy, 1.1 had other prodromal findings, and 0.8 had hematologic abnormalities. Prevalence of serum antibodies to HTLV-III/LAV, measured by an enzyme-linked immunosorbent assay, increased from 4.5% in 1978 to 67.4% in 1984. Of 31 persons who were seropositive and without the syndrome between 1978 and 1980, 2 developed the syndrome and 8 developed related conditions during a median follow-up of 61 months. Over a 6-year period, two thirds of cohort members were infected with HTLV-III/LAV and almost one third developed related conditions.

Risk factors for human immunodeficiency virus (HIV) infections in homosexual men.

To clarify risk factors for infection with the human immunodeficiency virus (HIV) we selected at random 785 homosexual men who had participated in studies of hepatitis B in San Francisco in 1978-80 for a follow-up study of the acquired immunodeficiency syndrome. Although most had not been contacted in over five years, 492 (63 per cent) were located and enrolled. The 240 (67 per cent) who had developed antibodies to HIV, as measured by an enzyme-linked immunosorbent assay (ELISA), were compared with 119 who had remained seronegative. In multivariate analyses, receptive anal intercourse with ejaculation by nonsteady sexual partners, many sexual partners per month, and other indicators of high levels of sexual activity were highly associated with seroconversions. None of the sexual practices that we studied appeared to offer protection against HIV infection.

Cluster of Cases of the Acquired Immune Deficiency Syndrome Patients Linked by Sexual Contact

The possibility that homosexual men with the acquired immune deficiency syndrome (AIDS) had been sexual partners of each other was studied. Of the first 19 homosexual male AIDS patients reported from southern California, names of sexual partners were obtained for 13. Nine of the 13 patients had sexual contact with one or more AIDS patients within five years of the onset of symptoms. Four of the patients from southern California had contact with a non-Californian AIDS patient, who was also the sexual partner of four AIDS patients from New York City. Ultimately, 40 patients in 10 cities were linked by sexual contact. On the basis of six pairs of patients, a mean latency period of 10.5 months (range seven to 14 months) is estimated between sexual contact and symptom onset. The finding of a cluster of AIDS patients linked by sexual contact is consistent with the hypothesis that AIDS is caused by an infectious agent.

Mapping a social network of heterosexuals at high risk for HIV infection

Objective:To determine how heterosexuals at risk for HIV infection interconnect in social networks and how such relationships affect HIV transmission. Design:Cross-sectional study with face-to-face interviews to ascertain sociosexual connections; serologic testing. Participants:Prostitute women (n=133), their paying (n=129) and non-paying (n=47) male partners; injecting drug users (n= 200) and their sex partners (n=41). Participants were recruited in sexually transmitted disease and methadone clinics, an HIV-testing site, and through street outreach in Colorado Springs, Colorado, USA. Main outcome measures:Reported behaviors, risk perceptions, sociosexual linkages, and HIV prevalence. Results:Respondents were well informed, but reported engaging in high-risk behaviors frequently. Nevertheless, over 70% of respondents perceived themselves to be at low risk for HIV infection. The 595 respondents identified a social network of 5162 people to which they belonged. Network analytic methods indicated 147 separate connected components of this network; eight of the 19 HIV-positive individuals in the network were located in smaller components remote from the largest connected component. Conclusion:The isolated position of HIV-positive individuals may serve as a barrier to HIV transmission and may account for the lack of diffusion of HIV in heterosexual populations in this region. Network analysis appears useful for understanding the dynamics of disease transmission and warrants further development as a tool for intervention and control.

Pathways to prostitution: The chronology of sexual and drug abuse milestones

To assess the sequence, timing, and prevalence of sexual and illegal drug use milestones in prostitute women, we interviewed 237 prostitutes in the community and 407 comparison women at an STD clinic. Drug use was more commonly reported by prostitutes than comparisons (86% vs. 23%), as was non‐consensual prepubertal sex (32% vs. 13%). Sexual‐ and drug‐related milestones occurred in the same order in both groups, with drug use preceding sexual activity and injecting drug use preceding prostitution. Ninety‐four percent of prostitutes who injected drugs reported noninjectable drug use before prostitution, and 75% of prostitutes who injected drugs reported doing so before beginning prostitution. The age distributions at critical events were similar for prostitutes and comparison women who reported regular drug use. Comparison women who did not report regular drug use were in general older than both these groups at the time of early sexual experience and drug experimentation. However, the ordering of these eve...

Choosing a centrality measure: Epidemiologic correlates in the Colorado Springs study of social networks☆

Abstract In a continuing analysis of a large network of persons who practice risky behaviors in an area of low prevalence for HIV transmission, we compared eight measures of centrality. Although these measures differ in their theoretical formulation and their distributional forms, they demonstrated substantial concordance in ranking as noncentral all but one of the HIV-positive persons in a large connected component of 341 persons, providing further support for the role of network structure in disease transmission.